Many attempts have been made to increase the dispersibility of fillers in polymer compositions. A common method for doing this is to modify the polymer with a functional group that interacts with the filler. Note, for example, U.S. Pat. No. 6,369,167, Patent Application Publication No. 2009/0163668, and U.S. Pat. No. 6,255,404, the disclosures of which are incorporated by reference. Silica fillers, in particular, impart desirable properties to polymers, especially those adapted to tire use. However, the use of silica fillers in polymers can also result in special problems relating to dispersibility and processability. Modifications to polymers to improve silica interaction with the polymer can have adverse effects on the polymer's interaction with carbon black, which also imparts desirable polymer properties to polymers, especially adapted to tire use. Therefore, functional group modification of polymers must produce satisfactory interaction with a variety of fillers. However, this functional group termination may also result in an increase in the Mooney viscosity of the treated polymers (hereinafter the use of Mooney viscosity will refer to conventional Mooney ML1+4/100 viscosity measures unless otherwise indicated). Note, for example, U.S. Pat. Nos. 5,659,056; 6,255,404; and 7,342,070, the disclosures of which are incorporated by reference. And Mooney viscosity creep with aging has become even more pronounced with the movement from batch to continuous polymerization. Note also, for example, U.S. Pat. Nos. 3,244,644 and 4,185,042, the disclosures of which are incorporated by reference.
As described above, the polymers are typically terminated using a number of different functional compounds including silane containing compounds to yield silane end-capped polymers. However, upon subsequent desolventization of the alkoxysilane terminated polymers through the use of either steam or heated water, an even larger increase in Mooney viscosity often occurs during the hydrolysis of alkoxysilane end groups thereby leading to coupling of the polymer via formation of Si—O—Si bonds between two end groups. Accordingly, it has been found that many of the processes tried in the past do not actually prevent an increase in Mooney viscosity, but only slow the rate of the hydrolysis reaction and, therefore, the rate of coupling of the polymer. Over a period of time, the slow hydrolysis of the end groups will occur, thereby continuing the problem of increased Mooney viscosity and coupling of the alkoxysilane terminated polymers with aging. Aging of polymers result in issues with rubber consistency, ease of mixing, etc.
Thus, while attempts have been made in the art to improve polymer interaction with various fillers, and improve processability of the polymers, a way to slow down the rate of the hydrolysis reaction and coupling of the alkoxysilane terminated polymers is still needed.